1. Field of the Invention
The present invention relates generally to sash windows, and more particularly to a single-hung or double-hung window having at least two sashes supported in vertical juxtaposition within a window frame.
2. Description of Related Art
Sash windows adapted to be mounted in an opening in the exterior wall of a commercial or residential building are known as single- or double-hung windows having a pair of upper and lower sashes. Among these windows, an improvement has been proposed which comprises a sash pivotable in an inward direction (room interior side) for enabling access for cleaning to an outside surface of the sash from the room interior side (U.S. Pat. No. 6,826,871 B2).
The sash described in U.S. Pat. No. 6,826,871 B2 is sidable in a vertical direction along jamb members of a window frame between a fully closed position and a fully open position. The sash is also inwardly pivotable about pivot shafts provided at a lower end portion thereof. The sash has a support mechanism disposed on a corner portion at the bottom thereof. The support mechanism generally comprises a slide shoe slidable in a vertical direction along each jamb member while engaging the jamb member, and a pin (pivot shaft) pivotally connecting the slide shoe and the bottom corner portion of the sash. The sash further has a guide member (latch mechanism) disposed on a corner portion at the top thereof. The guide member is normally disposed in guided engagement with each jamb member so that the top corner portion of the sash is guided along the jamb member during vertical sliding movement of the sash.
The guide member also constitutes a latch mechanism so as to permit inward pivotal movement of the sash. To this end, the guide member includes a body attached to the sash, a latch bolt projecting from the body for interlocking engagement with the jamb member, and a spring for urging the latch bolt in a projecting direction. The latch bolt is connected to a knob which is disposed on an outer surface of the sash at the room interior side. With this arrangement, the knob is manually operated to move the latch bolt into the body against the force of the spring, thus releasing the latch bolt from interlocking engagement with the jamb member. The sash is now allowed to undergo inward pivotal movement relative to the window frame.
The sill member has a first stopper member disposed on a top wall of the sill member, and a bottom rail of the sash has a second stopper member projecting downwards. The second stopper member is arranged such that it is vertically overlapped with the first stopper member at a position inwards of the first stopper member when the sash window is fully closed. With this arrangement, the first and second stopper members cooperate to limit deflection of the sash under high negative wind loads.
Another prior proposed improvement, such as disclosed in U.S. Pat. No. 6,243,999 B1, provides a sash window having a reinforcement mechanism for preventing the sash window from blowing outward during extreme storms. In the sash window, the reinforcement mechanism comprises a tongue-and-groove fitting structure formed jointly by a ridge or rib and a groove or recessed portion disposed between a bottom surface of the bottom rail of a sash and a top surface of the sill member of a window frame. When the sash is subjected to high positive wind loads or negative wind loads during extreme storms, the rib and the recessed portion engage together to thereby prevent the sash from blowing inward or outward under such high wind loads.
As for materials for frame members of the sashes, woods or synthetic resin materials such as polyvinyl chloride (PVC) are used in many cases in North America. In order to increase the strength of PVC sash frame members, a reinforcement member having a highly rigid cross-sectional shape is disposed inside a hollow frame member, such as described in U.S. Pat. No. 6,003,277.
According to U.S. Pat. No. 6,003,277, the hollow PVC sash frame and the PVC reinforcement member disposed inside the PVC sash frame are formed concurrently by a so-called “co-extrusion” process so that they are integrally connected together. The reinforcement member is hollow and has a particular cross-sectional shape that can provide high rigidity. An internal space of the hollow reinforcement member may be filled with another reinforcement member of PVC to provide an additional strength to the fame member.
The prior proposals discussed above are not fully satisfactory at least in terms of reinforcement or strengthening of sash windows against wind loads or impacts from flying objects during extreme storms.